SQLite Helper (C#) zt

时间：2014-05-23 12:08:00 收藏：0 阅读：558

http://www.codeproject.com/Articles/746191/SQLite-Helper-Csharp

This small class (SQLiteHelper.cs) is built on top of System.Data.SQLite.DLL. A reference of this DLL must be added into your projects.

Download: https://system.data.sqlite.org

List of Simplified Functions

GetTableStatus
GetTableList
GetColumnStatus
CreateTable
UpdateTableStructure
BeginTransaction, Commit, Rollback
Select
Execute
ExecuteScalar
Escape
Insert
Update
LastInsertRowId
RenameTable
CopyAllData
DropTable
ShowDatabase
AttachDatabase, DetachDatabase

Getting Start

Add this using statement at the top of your class:

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using System.Data.SQLite;

SQLiteConnection and SQLiteCommand have to be initialized before using SQLiteHelper:

Example:

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using (SQLiteConnection conn = new SQLiteConnection("data source=C:\\data"))
{
    using (SQLiteCommand cmd = new SQLiteCommand())
    {
        cmd.Connection = conn;
        conn.Open();
 
        SQLiteHelper sh = new SQLiteHelper(cmd);
 
        // do something...

        conn.Close();
    }
}

1. GetTableStatus

Get all information of tables in the database.

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DataTable dt = sh.GetTableStatus();

Sample result:

type	name	tbl_name	rootpage	sql
table	sqlite_sequence	sqlite_sequence	3	CREATE TABLE sqlite_sequence(name,seq)
table	person2	person2	5	CREATE TABLE "person2"( id integer primary key autoincrement, name text, tel text, email text, job text, remarks text)
table	player	player	4	CREATE TABLE `player`( id integer primary key autoincrement, lvl integer, weaponid integer, teamid integer, location text, team_name text, remarks text)
table	product	product	6	CREATE TABLE "product"( id integer primary key autoincrement, name text, qty integer)

2. GetTableList

Get a list of tables in database.

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DataTable dt = sh.GetTableList();

3. GetColumnStatus

Get all information of columns in specific table.

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// Get column‘s information from table "person"
DataTable dt = sh.GetColumnStatus("person");

Sample Result:

cid	name	type	notnull	dflt_value	pk
0	id	integer	0		1
1	lvl	integer	0		0
2	weaponid	integer	0		0
3	teamid	integer	0		0
4	location	text	0		0
5	team_name	text	0		0
6	remarks	text	0		0

4. CreateTable

Create table.

Example table structure: Person

Column Name	Data Type	Primary Key	Auto Increment	Not Null	Default Value
id	int	true	true
name	text
membershipid	int
level	decimal				5.5

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SQLiteTable tb = new SQLiteTable("person");
 
tb.Columns.Add(new SQLiteColumn("id", true));
tb.Columns.Add(new SQLiteColumn("name"));
tb.Columns.Add(new SQLiteColumn("membershipid", ColType.Integer));
tb.Columns.Add(new SQLiteColumn("level", ColType.Decimal, false, false, "5.5"));
 
sh.CreateTable(tb);

5. UpdateTableStructure

As the name said, it is used to update a table‘s structure. Maybe you have added new columns, or drop/deleted some columns. This method helps you to update it.

The process at code behind:

Assume that the old table is named: person
The class creates a temporary table (named: person_temp) with your new defined structure.
Copy all rows from person to person_temp.
Drop/delete table of person.
Rename table of person_temp to person

Code example:

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SQLiteTable tb = new SQLiteTable();
tb.Columns.Add(new SQLiteColumn("id", true));
tb.Columns.Add(new SQLiteColumn("name"));
tb.Columns.Add(new SQLiteColumn("sku"));
tb.Columns.Add(new SQLiteColumn("code"));
tb.Columns.Add(new SQLiteColumn("category"));
tb.Columns.Add(new SQLiteColumn("remarks"));

sh.UpdateTableStructure("person", tb);

6. BeginTransaction, Commit, Rollback

What is transaction?

By default, every SQL query that is sent to SQLite database engine happens in a transaction. The engine automatically BEGIN a transaction and COMMIT it at the end. COMMIT is something like "Make it take effect".

If we send 3 SQL queries (INSERT, UPDATE, DELETE, etc...), 3 transactions are taken place. According to [SQLite official documentation - Frequently Asked Questions]:

"...A transaction normally requires two complete rotations of the disk platter, which on a 7200RPM disk drive limits you to about 60 transactions per second..."

Which means, with a 7200RPM hard disk, the best that we can do is 60 INSERTs (or UPDATE, DELETE, etc) per second.

But, If we manually issue a BEGIN TRANSACTION, all the queries will be wrapped in single transaction, then SQLite can execute huge amount of queries per second. Somebody said he can execute 10 million per second at [stackoverflow.com], but this is also depends on the speed of hard disk that you are using.

Code example with SQLiteHelper:

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sh.BeginTransaction();
 
try
{
    // INSERT.....
    // INSERT.....
    // UPDATE....
    // ... skip for another 50,000 queries....
    // DELETE....
    // UPDATE...
    // INSERT.....

    sh.Commit();
}
catch
{
    sh.Rollback();
}

ROLLBACK, in the above example means Cancel Transaction. All queries that have sent to SQLite database within that specific transaction are dismissed.

7. Select

Return the query result in DataTable format.

Select(string sql)
Select(string sql, Dictionary<string, object> dicParameters = null)
Select(string sql, IEnumerable<SQLiteParameter> parameters = null)

Example 1:

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DataTable dt = sh.Select("select * from person order by id;");

Example 2 (With parameters support):

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var dic = new Dictionarystring, object();
dic["@aaa"] = 1;
dic["@bbb"] = 1;
DataTable dt = sh.Select("select * from member where membershipid = @aaa and locationid = @bbb;", dic);

Example 3 (With parameters support):

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DataTable dt = sh.Select("select * from member where membershipid = @aaa and locationid = @bbb;",
    new SQLiteParameter[] { 
        new SQLiteParameter("@aaa", 1),
        new SQLiteParameter("@bbb", 1)
    });

8. Execute

Execute single SQL query.

Execute(string sql)
Execute(string sql, Dictionary<string, object> dicParameters = null)
Execute(string sql, IEnumerable<SQLiteParameter> parameters = null)

Example:

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sh.Execute("insert into person(name)values(‘hello‘);");

9. ExecuteScalar

Return the result of first row first column in specific data type.

ExecuteScalar(string sql)
ExecuteScalar(string sql, Dictionary<string, object> dicParameters = null)
ExecuteScalar(string sql, IEnumerable<SQLiteParameter> parameters = null)
ExecuteScalar<datatype>(string sql)
ExecuteScalar<datatype>(string sql, Dictionary<string, object> dicParameters = null)
ExecuteScalar<datatype>(string sql, IEnumerable<SQLiteParameter> parameters = null)

Example:

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string a = sh.ExecuteScalar<string>("select ‘Hello!‘;");

int b = sh.ExecuteScalar<int>("select 1000;");

decimal c = sh.ExecuteScalar<decimal>("select 4.4;");

DateTime d = sh.ExecuteScalar<DateTime>("select date(‘now‘);");

byte[] e = sh.ExecuteScalar<byte[]>("select randomblob(16);");

10. Escape

Escape string sequence for text value to avoid SQL injection or invalid SQL syntax to be constructed.

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sh.Execute("insert into person(name) values(‘" + Escape(input) + "‘);");

11. Insert

Insert new row of data. All data will be added as parameters at code behind. This support blob (byte[]) value too.

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var dic = new Dictionary<string, object>();
dic["name"] = "John";
dic["membershipid"] = 1;
dic["level"] = 6.8;
 
sh.Insert("person", dic);

12. Update

Update row. All data will be added as parameters at code behind. This support blob (byte[]) value too.

Example 1: Update with single condition (where id = 1)

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var dicData = new Dictionary<string, object>();
dicData["name"] = "no name";
dicData["membershipid"] = 0;
dicData["level"] = 5.5;
 
sh.Update("person", dicData, "id", 1);

Example 2: Update with multiple condition (where membership = 1 and level = 5.5 and teamid = 1)

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var dicData = new Dictionary<string, object>();
dicData["name"] = "no name";
dicData["status"] = 0;
dicData["money"] = 100;
dicData["dateregister"] = DateTime.MinValue;
 
var dicCondition = new Dictionary<string, object>();
dicCondition["membershipid"] = 1;
dicCondition["level"] = 5.5;
dicCondition["teamid"] = 1;
 
sh.Update("person", dicData, dicCondition);

13. LastInsertRowId

Get the last issued id (Auto-Increment)

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sh.Insert("person", dicData);
long id = sh.LastInsertRowId();

14. RenameTable

Rename a table.

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sh.RenameTable("person", "person_backup");

15. CopyAllData

Copy all data from one table to another.

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sh.CopyAllData("person", "person_new");

Before copying, SQLiteHelper will scan the two tables for match columns. Only columns that exist in both tables will be copied.

16. DropTable

Drop table, delete a table

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sh.DropTable("person");

17. ShowDatabase

Display attached databases.

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DataTable dt = sh.ShowDatabase();

18. AttachDatabase, DetachDatabase

Attach or detach a database

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sh.AttachDatabase("C:\\data2013.sq3", "lastyeardb");
sb.DetachDatabase("lastyeardb");

That‘s it, guys/girls. Comments are welcome.

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